batch array: assert elements are objects

abstract-leveldown.js

@@ -161,11 +161,11 @@ AbstractLevelDOWN.prototype.batch = function (array, options, callback) {
   if (!options || typeof options != 'object')
     options = {}
 
-  var serialized = []
+  var serialized = new Array(array.length)
 
   for (var i = 0; i < array.length; i++) {
-    if (typeof array[i] !== 'object')
-      continue
+    if (typeof array[i] !== 'object' || array[i] === null)
+      return callback(new Error('batch(array) element must be an object and not `null`'))
 
     var e = Object.assign({}, array[i])
     var err
@@ -181,7 +181,7 @@ AbstractLevelDOWN.prototype.batch = function (array, options, callback) {
     if (e.type !== 'del')
       e.value = this._serializeValue(e.value)
 
-    serialized.push(e)
+    serialized[i] = e
   }
 
   if (typeof this._batch == 'function')

abstract/batch-test.js

@@ -84,6 +84,18 @@ module.exports.args = function (test) {
       t.end()
     })
   })
+
+  ;[null, undefined, 1, true].forEach(function (element) {
+    var type = element === null ? 'null' : typeof element
+
+    test('test batch() with ' + type + ' element', function (t) {
+      db.batch([element], function (err) {
+        t.ok(err, 'got error')
+        t.equal(err.message, 'batch(array) element must be an object and not `null`', 'correct error message')
+        t.end()
+      })
+    })
+  })
 }
 
 module.exports.batch = function (test) {